Wireless communication networks incorporating one or more mobile devices have become increasingly widespread in recent years. Retail stores and warehouses, for example, may use such communication networks with mobile data terminals to track inventory and replenish stock. The transportation industry may use such networks at large outdoor storage facilities to keep an accurate account of incoming and outgoing shipments. In manufacturing facilities, such networks are useful for tracking parts, completed products and defects. Such networks are also utilized in cellular telephone communications to allow users with wireless telephones to roam across large geographic regions while retaining telephonic access. Paging networks also utilize wireless communication networks which enable a user carrying a pocket sized pager to be paged anywhere within a geographic region.
Conventional wireless communication networks such as those referred to above typically involve a cellular network. As is known, cellular networks includes a number of fixed base stations interconnected by a cable medium often referred to as a system backbone. Associated with each base station is a geographic cell. Such cell is a geographic area in which an base station has sufficient signal strength to transmit data to and receive data from a mobile device such as a mobile data terminal or telephone with an acceptable error rate. Typically, base stations will be positioned along the backbone such that the combined cell area coverage from each base station provides full coverage of a building or site. The base stations may be connected via a hardwire connection to the system backbone, or may be connected via a wireless medium as is known.
Mobile devices such as telephones, pagers, personal digital assistants (PDAs), data terminals, etc. are designed to be carried throughout the system from cell to cell. Each mobile device is capable of communicating with the system backbone via wireless communications between the mobile device and a base station to which the mobile device is registered. As the mobile device roams from one cell to another, the mobile device will typically deregister with the base station of the previous cell and register with the base station associated with the new cell.
In order to provide sufficient cell area coverage, base stations within the cellular communication system typically are distributed at separate physical locations throughout an entire geographical region. Even still, it is possible that a mobile device may not be able to register with a base station and/or may lose its communication link with a base station. For example, an established communication link between the mobile device and a base station may incur a sudden increase in noise or interference. Alternatively, a mobile device may wander out of range of any base stations, for example. In such cases the mobile device becomes "distressed" in that communication directly with the system backbone via the base station no longer exists, at least temporarily.
In view of shortcomings such as those discussed above, there is a strong need in the art for a wireless communication network and emergency routing protocol which enables emergency communications between a distressed mobile device and the system backbone. Particularly, there is a strong need for an emergency routing protocol which is transparent to base stations so as to obviate a need to reconfigure operation of the base stations. Furthermore, there is a strong need for an emergency routing protocol which can utilize standard packet format within an existing system so as to eliminate a need for extensive changes in the system.